The biological treasures that were nurtured include genes that
facilitate the trapping of prey, the digestion of proteins and the
transport of small bits of protein — derived from the
bladderwort’s victims — from one cell to another.

“What’s exciting is that we didn’t go in and
cherry pick these genes,” says Victor Albert, professor of
biological sciences in the UB College of Arts and Sciences.
“We used bioinformatics to identify genes that were preserved
and enriched in the species, and when we did that, these genes
related to a carnivorous lifestyle were the ones that stood out.
They were screaming out at us, telling us to look at
them.”

“Through careful analysis, we were able to uncover the
genetic signatures of a carnivorous plant,” says Stephan C.
Schuster, professor of biological sciences at Nanyang Technological
University in Singapore.

The findings were published May 15 in the Proceedings of the
National Academy of Sciences, U.S.A. Albert and Schuster
co-led the study along with Luis Herrera-Estrella of the Center for
Research and Advanced Studies (Cinvestav) in Mexico. Other
researchers came from San Diego State University, El Instituto de
Ecología in Mexico, the University of Ottawa in Canada and
the Fujian Agriculture and Forestry University in China.

The genetic underpinnings of a predatorial plant

Albert, Schuster, Herrera-Estrella and colleagues first reported
sequencing the bladderwort genome in 2013, an achievement described
in the journal Nature.

However, with new tools available in the field of genomics, the
researchers joined forces again to create an even better version of
the bladderwort genome for the 2016 study.

The sequencing technique they chose was a single-molecule method
developed by Pacific Biosciences (PacBio). Like other technologies,
this one reads different sections of DNA in the genome, and then
specialized software combines overlapping chunks to form bigger and
bigger chains. But the PacBio method enabled the scientists to
build a better genome by generating individual strings of
bladderwort DNA more than 40 times longer than before.

This new, high-quality sequence allowed researchers to
scrutinize the bladderwort genome in new ways.

They were able, for instance, to identify important strings of
gene copies known as tandem repeats. These are fragments of genetic
material that were accidentally duplicated next to each other,
sometimes more than once. Such repeated genes are often lost over
time as a species evolves, so the ones that are retained are
candidates for having leant their hosts an evolutionary
advantage.

That’s especially true of the bladderwort, Albert and
colleagues say. They note the plant has a tiny,
gene-rich genome, an indication the species has had a history
of rampant DNA deletion.

Tandem repeats in the bladderwort genome included genes
responsible for the creation of papain proteases —
“proteins that chew up other proteins,” as Albert puts
it — as well as genes that promote peptide transport, in
which chopped-up proteins (parts of victims) are shuttled from one
bladderwort cell to another. Both groups of genes are highly active
in the plant’s vacuum traps, hinting at a role in the
digestion of prey.

Tandem repeats also included genes tied to traits such as the
acidity of the traps and the elasticity of their cell walls —
qualities that may facilitate the plant’s effectiveness as a
predator.

“The trap of Utricularia is only two cells thick,
and the way it does its trapping is it creates a whole lot of
negative pressure inside the trap to suck in the prey once
triggered,” Hererra-Estrella says. “The cell walls are
under a lot of tension. So it’s no shock at all that there
seem to be some interesting clusters of tandem duplicates that deal
with the cell wall dynamism.”